Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$70.63	10.610%	$78.1238	$78.12	$78.10	$78.10
Purchase #2	$50.63	11.306%	$56.3542	$56.35	$56.35	$56.40
Purchase #3	$116.34	12.494%	$130.8755	$130.88	$130.90	$130.90
Purchase #4	$56.59	9.712%	$62.086	$62.09	$62.10	$62.10
Purchase #5	$129.50	11.486%	$144.3744	$144.37	$144.35	$144.40
Purchase #6	$198.72	11.315%	$221.2052	$221.21	$221.20	$221.20
Purchase #7	$216.63	12.768%	$244.2893	$244.29	$244.30	$244.30
7 purchase totals =	$839.04		$937.3084	$937.31	$937.30	$937.40